This invention relates generally to compounds, compositions, devices, and methods useful for detecting the presence of leukocytes through the activity of leukocyte esterases and proteinases in urine.
The presence of leukocytes in human urine is associated with infection or malfunction in the kidney or urinary tract. Accurate detection has a significant meaning for the physiological treatment or diagnosis of the patient.
A basic method to measure the number of leukocytes in urine by microscope has been widely available for some time. However, the disadvantages of this method include the investment of time and money in obtaining and installing the appropriate instrumentation. Further, false negatives can be obtained when samples are allowed to sit too long before analysis.
Research has been directed to developing other methods, such as indicator assays, that are suitable for detecting leukocytes more easily, conveniently, and accurately. Typical indicator assays use a specific chemical substance (e.g., a substrate) that is degraded by one or more enzymes present in leukocytes to create a product suitable for effectuating a visible color change.
One such leukocyte assay is disclosed in U.S. Pat. No. 3,087,794 and involves the use of peroxidase that is contained in a granular leukocyte. This assay includes a filter paper stained with hydrogen peroxide and o-tolidine, which shows a colored oxidative product when contacted with leukocytes. Yet this assay is less than desirable because peroxidase can be dangerous and reductive materials in urine may make actual application impractical.
Other methods designed to confirm the presence of esterase and proteinase in leukocytes have also been developed. For example, one method uses a colorless or pale-colored ester compound as a substrate that is degraded by esterase into a colorless acid moiety and an alcoholic moiety. Then, under diazonium or oxidative reaction, the alcoholic moiety is converted to a second densely colored product. This method was derived from a process in which enzymatic degradation of the substrate naphtol-AS-D chloroacetate produced chloroacetate and naphtol-AS. Reaction of the naphtol-AS product with a diazonium salt resulted in the formation of a colored azo compound.
This assay allows for the determination of leukocyte concentration by the naked eye. Yet the use of this assay is less than desirable because the diazonium salt may react with urobilinogen or bilirubin contained in urine. As a result, concentrations of leukocytes greater than 500 cells/xcexcl are often necessary to avoid a false-negative reading.
U.K. Patent No. 1,128,371 discloses other possible substrates, i.e., colorless indoxyl or thioindoxylesters. These substrates are degraded into indoxyl or thioindoxyl by esterase. Colored indigo or thioindigo may then be produced by reaction with oxygen in the air or by an oxidizer. Yet the use of an assay with these substrates is less than desirable because this is not sensitive and fails to detect leukocytes at a concentration less than 10,000 cells/xcexcl.
Similarly, U.S. Pat. No. 4,278,763 suggests indoxyl-type substrates by disclosing a method of using indoxyl or thioindoxylamino acid ester as a substrate.
Other assays using pyrrole derivatives as substrates have also been disclosed. For example, U.S. Pat. No. 4,704,460 discloses use of an amino acid ester of a pyrrole derivative as a substrate. When this derivative is degraded in the presence of diazonium salt, a change in sample color to deep violet results. Moreover, the addition of a nucleophilic alcohol, such as decanol, greatly facilitates reaction rate, and in turn, allows detection of leukocyte concentrations as low as 10 cells/xcexcl within 90 seconds. Yet this assay is less than desirable because the syntheses of these two substrates is very difficult.
The above-described assays are characterized by numerous disadvantages. Some disadvantages include the detection of false negatives, the interference of urobilinogen or bilirubin, the lack of sensitivity, and the requirement of less-than-desirable substrates. Thus, it would be desirable to identify new compounds and methods of using the compounds to detect the presence of leukocytes in urine.
The invention is directed to thiazole esters suitable for detecting leukocytes in urine, compositions containing thiazole esters, diagnostic devices suitable for detecting leukocytes in urine, and methods of using the thiazole esters or compositions thereof for detecting leukocytes in urine.
In one aspect, this invention is directed to novel thiazole esters.
One thiazole ester according to this invention is of the formula: 
or a salt or solvated salt thereof, in which
A is an N-blocked amino acid residue or an N-blocked peptide chain, preferably N-blocked alanine or N-blocked polyalanine; and
R1 is unsubstituted or substituted heteroaryl; alkenyl substituted with unsubstituted or substituted aryl; or alkenyl substituted with unsubstituted or substituted heteroaryl. For example, R1 may be thienyl, pyridyl, furyl, styryl, pyrrolyl, or indolyl.
Another thiazole ester according to this invention is of the formula: 
or a salt or solvated salt thereof, in which
A is an N-blocked amino acid residue or an N-blocked peptide chain, preferably N-blocked alanine or N-blocked polyalanine; and
R2 is unsubstituted or substituted fused hydrocarbyl rings in which at least one ring is aromatic. For example, R2 may be naphthyl or anthryl.
In another aspect, this invention is directed to compositions that include a thiazole ester of formula I or II. Compositions of the invention may also include a diazonium salt such as 2-methoxy-4-morpholinobenzene diazonium chloride, zinc chloride double salt.
In still another aspect, this invention is directed to diagnostic devices that include a compound or composition of the invention. Such diagnostic devices include a substrate having a thiazole ester of formula I or II deposited thereon.
The compounds, compositions, and diagnostic devices of the invention are also suitable for use in methods for detecting leukocytes in urine. Methods for detecting leukocytes in urine include contacting a thiazole ester of the invention and a diazonium salt with a urine sample.
The compounds and compositions suitable for use in devices and methods of the invention are typically pharmaceutically acceptable.
The invention is directed to detecting leukocytes in urine. The presence of leukocytes is typically detected by detecting the presence of enzymes known in the art as leukocyte esterases and leukocyte proteinases that are present with leukocytes.
Compounds of the invention include thiazole esters that contain an ester functionality, which is hydrolyzed upon exposure to leukocytes in urine. The hydrolysis of the ester of a thiazole ester of the invention provides a useful diagnostic technique because thiazolyl can react with a diazonium salt to produce an azo dye.
The compounds according to this invention are thiazole esters that are suitable for use in compositions, diagnostic devices, and methods that can be used to detect leukocytes in urine.
One thiazole ester suitable for use in compositions and methods of the invention is of the formula: 
or a salt or solvated salt thereof, in which A is an N-blocked amino acid residue or an N-blocked peptide chain, preferably N-blocked alanine or N-blocked polyalanine (e.g., alanine-alanine, alanine-alanine-alanine, and the like), being blocked at the amino terminus by protecting groups known in the art, such as, for example, benzyloxycarbonyl, t-butoxycarbonyl, and p-toluenesulfonyl; and R1 is unsubstituted or substituted heteroaryl; alkenyl substituted with unsubstituted or substituted aryl; or alkenyl substituted with unsubstituted or substituted heteroaryl.
The term xe2x80x9cheteroarylxe2x80x9d includes heterocyclic aromatic derivatives having at least one heteroatom, such as, for example, nitrogen, oxygen, phosphorus, or sulfur, and includes, for example, furyl, pyrrolyl, thienyl, oxazolyl, pyridyl, imidazolyl, thiazolyl, isoxazolyl, pyrazolyl, isothiazolyl, and the like. The term xe2x80x9cheteroarylxe2x80x9d also includes fused rings in which at least one ring is aromatic, such as, for example, indolyl, purinyl, benzofuryl, benzothienyl, quinolyl, 4,5,6,7-tetrahydro-1H-indolyl, and the like. In the case of fused rings that have a hydrocarbyl ring fused to a heterocyclic ring, such as, for example, benzothienyl and indolyl, the fused rings may be bonded to thiazolyl through either the hydrocarbyl ring or the heterocyclic ring. In some embodiments, heteroaryl includes a 5-membered ring. In other embodiments, heteroaryl includes a 6-membered ring.
Such heteroaryl groups may be unsubstituted or substituted on the ring by, for example, aryl, heteroaryl, alkyl, alkenyl, alkoxy, amino, acyl, halo, nitro, cyano, xe2x80x94SO3H, or hydroxy, in which such substituents may further be substituted by aryl, heteroaryl, alkyl, alkenyl, alkoxy, amino, acyl, halo, nitro, cyano, xe2x80x94SO3H, or hydroxy. In some embodiments, heteroaryl is substituted with alkyl, such as methyl, ethyl, propyl, or butyl. In other embodiments, heteroaryl is substituted with alkoxy, such as methoxy, ethoxy, propoxy, or butoxy. In still other embodiments, heteroaryl is substituted with aryl or heteroaryl.
The term xe2x80x9carylxe2x80x9d includes aromatic hydrocarbyl, such as, for example, phenyl, including fused aromatic rings, such as, for example, naphthyl.
The term xe2x80x9calkylxe2x80x9d includes a straight or branched saturated aliphatic hydrocarbon chain having from 1 to 4 carbon atoms, such as, for example, methyl, ethyl, propyl, isopropyl (1-methylethyl), butyl, t-butyl (1,1-dimethylethyl), and the like.
The term xe2x80x9calkenylxe2x80x9d includes an unsaturated aliphatic hydrocarbon chain having from 2 to 4 carbon atoms, such as, for example, ethenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-methyl-1-propenyl, and the like.
The above alkyl or alkenyl groups may optionally be interrupted in the chain by a heteroatom, such as, for example, a nitrogen or oxygen atom, forming an alkylaminoalkyl or alkoxyalkyl group, for example, methylaminoethyl or methoxymethyl, and the like.
The term xe2x80x9calkoxyxe2x80x9d includes alkyl as defined above joined to an oxygen atom having from 1 to 4 carbon atoms in a straight or branched chain, such as, for example, methoxy, ethoxy, propoxy, isopropoxy (1-methylethoxy), butoxy, t-butoxy (1,1-dimethylethoxy), and the like.
The term xe2x80x9caminoxe2x80x9d includes a substituent of the formula xe2x80x94N(R3)2 in which each R3 is independently hydrogen or alkyl. The term xe2x80x9calkylxe2x80x9d is as defined above.
The term xe2x80x9calkenyl substituted with unsubstituted or unsubstituted arylxe2x80x9d or xe2x80x9calkenyl substituted with unsubstituted or substituted heteroarylxe2x80x9d includes alkenyl as defined above, and such groups are substituted with unsubstituted or substituted aryl or unsubstituted or substituted heteroaryl, respectively. The terms xe2x80x9carylxe2x80x9d and xe2x80x9cheteroarylxe2x80x9d are as defined above. Examples of suitable substituted alkenyls include styryl, cinnamyl, furylethenyl, pyridylethenyl, and thienylpropenyl.
In some embodiments, alkenyl substituted with unsubstituted or substituted aryl is alkenyl substituted with unsubstituted or substituted phenyl. This phenyl, in some embodiments, is substituted with alkoxy, such as methoxy, ethoxy, propoxy, or butoxy. In other embodiments, alkenyl substituted with unsubstituted or substituted heteroaryl is alkenyl substituted with a nitrogen-containing ring, oxygen-containing ring, or sulfur-containing ring.
Examples of R1 groups for thiazole esters suitable for use in compositions and methods of the invention include 2-thienyl; 4-pyridyl; 2-furyl; xcex2-styryl; 1,2-dimethyl-4-pyrrolyl; and 3-indolyl. It should be appreciated that one skilled in the art, having read this specification, would understand that a heteroatom may be at any one of several positions in a ring.
Another thiazole ester suitable for use in compositions and methods of the invention is of the formula 
or a salt or solvated salt thereof, in which A is an N-blocked amino acid residue or an N-blocked peptide chain, preferably N-blocked alanine or N-blocked polyalanine (e.g., alanine-alanine, alanine-alanine-alanine, and the like), being blocked at the amino terminus by protecting groups known in the art, such as, for example, benzyloxycarbonyl, t-butoxycarbonyl, and p-toluenesulfonyl; and
R2 is unsubstituted or substituted fused hydrocarbyl rings in which at least one ring is aromatic.
Fused hydrocarbyl rings include at least two hydrocarbyl rings that maintain at least one bond in common between the rings, for example, naphthyl, anthryl, 5,6,7,8-tetrahydronaphthyl, phenanthrenyl, triphenylenyl, 1H-fluorenyl, and the like. Fused hydrocarbyl rings may be substituted by, for example, aryl, heteroaryl, alkyl, alkenyl, alkoxy, amino, acyl, halo, nitro, cyano, xe2x80x94SO3H, or hydroxy, in which such substituents may further be substituted by aryl, heteroaryl, alkyl, alkenyl, alkoxy, amino, acyl, halo, nitro, cyano, xe2x80x94SO3H, or hydroxy. These substituents are as defined above.
In some embodiments, fused hydrocarbyl rings contain at least one 5-membered ring. In other embodiments, fused hydrocarbyl rings contain at least one 6-membered ring. In still some embodiments, fused hydrocarbyl rings are substituted on at least one ring with alkyl, such as methyl, ethyl, propyl, or butyl. In other embodiments, fused hydrocarbyl rings are substituted on at least one ring with alkoxy, such as methoxy, ethoxy, propoxy, or butoxy.
In one embodiment, R2 is 1-naphthyl.
A composition of the invention includes a thiazole ester of formula I or II. Such a composition may also include a diazonium salt such as 2-methoxy-4-morpholinobenzene diazonium chloride, zinc chloride double salt.
Compositions of the invention may be free of salts known in the art to have an accelerating action. Examples of salts that give an accelerating action include salts of monovalent and divalent cations of the alkali metals and alkaline earth metals, such as, for example, Li+, Na+, K+, and Mg++ as well as their typical anions.
A diagnostic device suitable for detecting leukocytes in urine includes a substrate suitable for supporting a thiazole ester of the invention, such as, for example, filter paper, filtration membrane, and other inert carriers. These substrates are known in the art. The diagnostic device also includes one or more thiazole esters of formula I or II. This compound is included with the substrate by, for example, sedimenting the derivative onto the substrate.
Generally, a novel diagnostic device may be prepared by combining the thiazole ester, an accelerator, and a diazonium salt. Accelerators suitable for use in compositions and methods of the invention are known in the art and include, for example, octanediol and decanol.
Diazonium salts suitable for use in compositions and methods of the invention are known in the art and include compounds that may be used for color-developing technology, such as, for example, 1-diazo-8-naphtol-3,6-disulfonic acid, chloride, zinc chloride double salt; 6-diazo-1-naphtol-3-sulfonic acid, chloride double salt; and 2-methoxy-4-morpholinobenzene diazonium chloride, zinc chloride double salt. Preferably, the diazonium salt used in accordance with the invention has no interaction with urobilinogen and/or bilirubin.
Methods for manufacturing a device according to this invention are known in the art. Generally, a first solution containing boric acid and polyvinylpyrrolidone is deposited onto a substrate, such as a filter paper. Then a second solution containing a thiazole ester of the invention and a diazonium salt, such as 2-methoxy-4-morpholinobenzene diazonium chloride, zinc chloride double salt, is deposited onto the substrate. Both solutions deposited onto the substrate may be free of a salt known in the art to have an accelerating action as described above.
To prepare a thiazole ester of the invention, a thiazolone derivative and an alanine or polyalanine derivative may be used as starting materials. Thiazolones may be synthesized by reacting carboxymethyl thiobenzimidate hydrobromide and pyridine.
As illustrated in the following scheme, the synthesis of a thiazole ester of the invention includes the reaction of a thiazolone derivative of the general formula (2), and an amino acid chloride of the general formula (3). 
Each starting material is dissolved in solvent, and the resulting solutions are cooled and mixed slowly. This reaction mixture is stirred and then allowed to stand at room temperature for several hours. The reaction mixture is then washed, dried, filtered, and concentrated under reduced pressure. The solid, so formed, is dissolved in acetone and hexane is added. To remove any resulting hemisolid impurity, the reaction mixture is allowed to stand at low temperature for about 1 hour. Another portion of hexane is added to the residue and the mixture is refrigerated for 10 hours. The desired product is then filtered and dried.
Thiazolone derivatives tend to be highly reactive, resulting in dimerization or multimerization even during recrystallization. This may lead to poor yield. Thus, for the current invention, pure substances are isolated from the final product of the synthesis of the thiazole ester without purifying thiazolone of the general formula (2). This method of synthesis enhances the yield of the derivatives of the invention.
In contrast to this, the aforementioned indole or pyrrole derivatives have some recognized disadvantages. Many side reactions occur in the process of manufacturing their intermediates. Moreover, the reaction mechanism is very complicated and the yield for indole and pyrrole derivatives proves to be poor. But the synthesis of the thiazole esters of this invention allows for larger amounts of final product to be produced by a general method within a relatively short period of time. Moreover, because the method of synthesizing the thiazole esters of the invention is relatively simple and general, mass-scale production is more practical.
Methods of the invention include detecting the presence of leukocytes in urine. To detect the presence of leukocytes in urine, a urine sample is contacted with a thiazole ester of the invention and a diazonium salt in the presence of an accelerator. If leukocytes are present, then a reaction between thiazolyl and the salt produces an azo dye having a violet color.
Typically such a method is directed to contacting a urine sample with a substrate, for example, filter paper, that has a first solution of boric acid and polyvinyl pyrrolidone deposited thereon and then a second solution of a thiazole ester of formula I or II; a diazonium salt; and an accelerator deposited thereon. This method may be carried out free of an accelerating salt. When a urine sample containing leukocytes contacts such a substrate, then a violet color, which appears on the substrate, is observed.